I wanted to come back and make a post, I just talked to another designer, to see if she was having the same issue.
Try checking your Magic Box Status! My Marketplace > Merchant Home > On the left side Magic Box Status
Scroll all the way down to the bottom of the page and you will see : Registered Servers
Now I just moved sims, so when I pulled this up I had 3 locations for my one box. I removed the 2 locations that were incorrect, and only left the one where my box is located now. I am testing this method to see if the problems clear up. Ive noticed if you move that box, its going to record every movement, and some of those need to be deleted bc the Marketplace cant communicate with a box that isnt there. I dont know if this works, granted I just got off IM with the other owner. Maybe it will and maybe it wont. I have like 200 something items loaded to the MP, she also suggested using multiple boxes. Also if it doesnt help, maybe taking the box back shutting off and then dropping it again, and resetting the box.
Ive dont all of the above, and will post tomorrow if the failed deliveries stop to give some feedback. Its an annoying issue, and I hope this helps anyone out there as frustrated as I was.